


Bred By An Alpha

by Everyday_Im_Preaching



Category: Gravity Falls
Genre: F/M, Intersex!Mabel, Mating Cycles/In Heat, Other, Rape/Non-con Elements, Top!Mabel, bottom!Bill, commission, hatefucking, ntgbd
Language: English
Status: Completed
Published: 2017-03-13
Updated: 2017-03-13
Packaged: 2018-10-04 07:06:56
Rating: Explicit
Warnings: Rape/Non-Con
Chapters: 1
Words: 3,138
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/10271033
Author URL: https://archiveofourown.org/users/Everyday_Im_Preaching/pseuds/Everyday_Im_Preaching
Summary: Going into heat is awful.Going into heat without your omega--that's horribly painful and unpleasant.But.When two alphas go into heat together, it's a disaster.





	

**Author's Note:**

  * Inspired by [Nowhere To Go But Down](https://archiveofourown.org/works/6403753) by [Everyday_Im_Preaching](https://archiveofourown.org/users/Everyday_Im_Preaching/pseuds/Everyday_Im_Preaching). 



> This is a commission piece! :)
> 
> THIS IS IN NO WAY PART OF THE CANON UNIVERSE.

  
It started out with play-wrestling.  
Erin and Dipper had left for the next week, taking advantage of a free trip to a skiing resort up north. They'd marked it an 'alpha-free' period of time, meant for relaxing. This left Mabel and Bill doing nothing but sitting on their hands waiting for their respective partners to return.  
Now...well, Mabel was straddling Bill, lips drawn back in a snarl. Bill's lips were drawn in reflex, mildly confused at the soft tingling that was rippling through him—it felt like heat. The need to rut was pooling in his belly, and judging by the pheromones that were rolling off of the other alpha, she was going into heat as well. At least some fucked up version of a preheat.

  
“Mabel, you need to get off of me.” Bill rumbled softly, unable to keep the challenge from his voice. He was rattled. Bill had heard the stories, of course, of alphas rutting each other in heat. It was possible, but he definitely didn't want those stories to come to life if he was involved. Mabel was leaning forward, hips rocking down against Bill and getting a low rumble from him. “Get off.” he snarled, thrashing in her grip and tossing her away with a thud.

  
“What the fuck.” Mabel snapped, flashing her fangs and dragging her claws against the hardwood. “What was that about?” she demanded, unmoving from her spot.

  
“You're going into heat, and fuck if I'm not too.” Bill growled at her, stumbling to his feet and trying to fight the sudden onslaught. “I'm not about to go at it like rabbits with you. We need to call Dipper and Erin, lock ourselves away until they get home.” he was searching his pockets for his cellphone, gritting his teeth as a wave of rage swam through him at the scent of another alpha in the room, and the need to dominate flooded his system.

  
Mabel was panting heavily from her spot on the floor, eyes pinched shut and tongue darting along her fangs to soothe their pain, no doubt. Bill's fingers shook as he attempted to type the message to Dipper, vision swimming. Behind him, Mabel was snarling and he swore. Female alphas were far more aggressive to other alphas from what he'd seen.

  
“You need to hold it together just a little bit longer, Mabel.” Bill told her, hitting the send just in time for Mabel to take him out at the knees; he landed on the floor, hard. Kicking out, he tried to free himself. Mabel let out a snarl, claws digging into Bill's dress pants and shredding them as her fingers climbed and ripped his belt free.

  
“Another alpha.” Mabel hissed; she must have been experiencing her preheat long before Bill had. She was looking at him with a critical eyes, nose scrunched in disgust. “You'll do for a quick heat fuck.” Bill bared his fangs and brought his knee up, hard, driving it into her stomach and throwing her off again—instead of leaving her there, he landed on her heavily, pinning to the floor.

  
“You think you're going to fuck me?” Bill snarled, gripping her wrists and pinning them to the floor. Mabel twisted beneath him, trying to break his hold while snapping and biting at him. “You better rethink that, bitch. You might be an alpha, but you're a female.” Bill shook his head, trying to regain his thoughts. “Mabel, I'm sorry, I didn't mean that.”  
Mabel snarled at him again, kicking her legs beneath him, but he held her still.

  
“Then lay down and let me fuck you, pretty boy.” Mabel hissed. “You're not even a real alpha; you're so whipped by your omega, you might as well be a beta.” Bill leaned over her, mouth inches from hers.

  
“I'm not going to devolve to calling names, I'm just going to make you submit the hard way.” he breathed. Mabel hissed at him, jerking her hips up. He pressed a kiss to the corner of her mouth, moving away just in time to avoid her fangs. “Going to knot you real pretty like.” he teased, getting an angry roar.

  
“Fuck you.”

  
“You'd make a pretty omega, you know.” Bill murmured, ignoring her anger. “Flushed and wet, begging for a cock to fill you. Not as pretty as my omega, of course. But I suppose there's enough of a resemblance.”

  
“Sick fuck.” Mabel whispered, eyes flashing.

  
“Poor little alpha, so mad. Maybe you shouldn't of tried to dominate me?” Bill questioned, drawing her hands above her head and pinning them there so he could clench her jaw. He jerked it to the side so he could press his nose against the side of Mabel's neck, licking her scent glands and getting an enraged howl.

  
With an unimaginable amount of strength, Mabel yanked her hands apart and out of Bill's hands. Bill let out an angry yelp as he was rolled over on to his back, the other alpha on top of him and furious. He was flipped on to his stomach in an instant, Mabel jerking her hips against his with a hiss. An elbow slammed between Bill's shoulderblades as he tried to rise, getting a pained whimper.

  
“Stay the fuck down.” Mabel hissed, tugging at the remnants of his pants and tossing them to the floor. “Think you can play with me like that?” Bill struggled as hands hauled his hips up. He lashed an arm out, fist smacking into Mabel's cheek and sending her tumbling away.

  
“I can, and I will.” Bill snarled, gathering his feet beneath him and catching Mabel head on as she charged at him. They struggled for a moment, before he was back on the floor. Bill let out a displeased whine; at another shove of her hips against him, he froze. “Wait.”

  
“Didn't know I had a cock, did you?” Mabel whispered, voice husky in Bill's ear as she laid over his back, folding one of his arms beneath his body and pinning the other above his head. Bill squirmed, digging his heels against the carpet and whining again. “Female alpha's have the luxury and shame of being intersex. And you're going to bow for me and take it. After all, you'd make the much better omega; shame you don't self-lubricate.”

  
Bill snarled and snapped at her as she tugged at his pants; now that she had him in a suiting pin, she seemed almost leisurely with her motions. Bill shuddered as his bare ass was exposed to the air—this caused him to struggle harder, voice rising into a roar.

  
“Don't worry, I'll get you nice and slick for me. You'd like that, wouldn't you? My little pseudo-omega, bet you really want a cock, despite how aggressive you are.” She smacked his ass sharply, getting a yelp. “Whore.”

  
“Fuck off.” Bill hissed, lashing out with a kick. Mabel avoided the limb and proceeded to slip a knee on the inside of his, pressing down hard. He let out a cry of pain, thrashing again.

  
“If you stop fucking moving this'll hurt less.” Mabel growled, voice guttural and filled with rage. “Just let me fuck you.”

  
“Never.”

  
“I wasn't giving you an option pretty boy.” She dug her knee in sharper, and he heard the familiar sound of a cap clicking open. “You're lucky I had this on me for Erin, or I'd be fucking you with spit.” Mabel told him, though she sounded more like she was talking to herself. “Don't want to hurt you too bad.” she continued to murmur, cradling his previously reddened skin. “Don't want to hurt you.” a gentle kiss was pressed to the back of his neck.

  
The lube was cold as it was drizzled between his ass cheeks, soon smoothed by two fingers, rubbing it against his clenched hole. It combated the heat in the area a tad bit, and when she added a bit more, he found his body relaxing against his will. She let out a pleased trill and began to press a finger inside—Bill yelped immediately and continued to whine in pain as she pressed hard on the arm behind his back.

  
“Easy.” Mabel hissed. “Just accept it like the little breeding-bitch you are.” she pressed it in farther, all the way up past the first and second knuckle until it was all the way in. It took all of half-a-minute before she was pulling it back out, eyes lighting up with the way that Bill's walls clung to her finger. With renewed vigour, she began to thrust it in and out, trilling as she loosened the older alpha up.

  
The need to dominate was flushing out of Bill's system as he laid there, thinking about how utterly fucked he was. The finger inside of him felt uncomfortable and wrong, but it was as if his heat had simply given up, whilst rationality had taken it's place. Bill couldn't escape Mabel's grip, he could only suffer through it—he wasn't sure if the other alpha had a knot, but he was certain that she'd be less apt to restrain him after fucking him once.

  
“Always was jealous of my brother. Having an alpha buy him like you did.” Mabel murmured, laying herself across his back as she pressed in a second finger. “Thought it was romantic, at first. But then I realised what a prick you are.” Bill shifted his hips uncomfortably, trying to keep his breath even and block out Mabel. The fingers surged deep, not giving him much time to adapt. Her small breasts drug over his back, nipples hard and firm as the pressed against his skin.

  
Sensing that he had no answer, Mabel crooked her fingers up, rubbing along his passage, searching for something. Bill's body jerked as they pressed against his prostate, pulling a low whimper from him. She trilled at him and brushed the small bud again and Bill let out a sob as pleasure slipped through him, pooling in his belly and getting his cock to twitch. His heat was reawakening at the pleasure, demanding to fuck, to cum. But not to flee the female alphas grip.

  
“You like that? I can give you more pleasure, just bare that little neck for me.” Mabel purred, rubbing his prostate again. Bill's body jerked, but he refused to move his head. The other alpha snickered and went back to the ruthless stretching from before, spreading her fingers in a wide scissor that left a subtle burn in their wake. “I'm going to put my cock in now.” she breathed into his ear, pulling her fingers out. “Nice thick one, just for you.”

  
At the words, Bill tried to twist away, making his distaste vocal—words escaped him and he had to rely on the primal cry to try and convey how he felt. It reminded him of how Dipper was in heat. God, Dipper. His perfect little omega; was he rushing home now? Or did he think that this was all a joke to get him to come home early?

  
Bill jerked even harder when he felt the head of Mabel's cock against his hole—he couldn't remember her jerking her pants down or slickening herself up but both seemed to have happened in the amount of time that he'd been thinking about her brother. He let out another pitiful whine, but he knew he'd lost this fight—hanging his head low, he braced himself for the other alpha to fuck him.

  
Mabel didn't stop until she was buried to the root, every bit of her cock shoved deep into the man beneath her. It hurt; the pain was near unbearable, with only the shame of letting himself be taken like this outweighing it. She didn't seem to mind his small whimpers of pain, because she yanked herself back before thrusting back in with a level of force that had Bill shaking. His heat clawed at his belly, demanding that he push his hips back and demand more, demand an orgasm—but he stood his ground. He wasn't going to beg like an omega. He was an alpha, damn it.

  
“It'll feel better soon.” Mabel promised, using the angle of their bodies to press in deep. “Wouldn't you like that? Your body is so hot and tight and needy. You'd like to cum, wouldn't you?” Bill shook his head; Mabel grunted, hips continuing to piston forward with deep, painful thrusts.

  
“You're hurting me.” Bill hissed suddenly, finding his voice.

  
“Just for a little while.” Mabel breathed, grunting happily. “You can handle a little bit of pain.” She straightened herself, using her free hand to grip his hip as she shunted him against the floor. His legs shook and he strained to push himself up from the wood but Mabel snarled, shoving him back down. “I can be a lot rougher, if you want.” she snarled.

  
“No, no, _no_.” Bill pleaded, gritting his teeth in between his words as they were punctuate with short, deep thrusts like a jackhammer. Pleased with his denial, she switched back to the smooth pace from before. His body began to adjust, but it still felt odd—he definitely wasn't prepared to live through this situation again.

  
And then one of her thrusts pressed against his prostate head-on, and his resolve to stay quiet dissolved into a puddle—he let out a low moan, unconsciously rocking his hips up in an attempt to get the alpha to hit the spot again. Mabel's hips stuttered for only a moment at the noise before she was slamming her hips forward, aiming for the same angle.

  
“There we go.” Mabel grunted, listening to the encouraging groans from beneath her; she let of Bill's arm so she could grip his hips fully, driving into him without reserve. “Good little breeding-bitch. Want my cum, don't you?” Bill didn't reply, swinging his arm beneath him so he could lessen his impact with the floor. Sweat poured down his face and body; he was overheating—he needed to –

  
A hand closed around his cock and he let out a relieving groan as it began to work him quickly.

  
“I've got you.” Mabel promised. And in that moment, Bill believed it. He surrendered to her then, baring his neck and fighting down the aggressive part of him. Getting through his heat was what was important right now. It wouldn't be long until he became like Mabel, a puppet controlled by lust—hopefully Dipper would come home before then.

  
Bill came with a cracked cry into Mabel's hand, her cock pressing hard against his prostate as she continued to hammer into him, chasing her own release. He slumped forward, letting the other alpha grip his hips tightly, grinding deep inside of him with careful swivels of her hips. Letting him know her intent to seed him. Bill didn't flinch, simply too tired and too content to do anything but gasp when Mabel came inside of him. She let out a quiet purr as she did so, laying her chest over Bill's back and licking at the back of his neck—but the cum just kept pouring into him. There was so much of it.

  
Bill shifted his hips, and she snarled, fangs nicking his neck. He froze; she had no knot to keep the release inside of him. Yet Mabel still refused to let him move, even as it became uncomfortable and heavy inside of him. He let out a whine of discontent, but found it hard to move from his place. The female alpha must have had something in her semen that incapacitated him.

  
It was a good ten minutes before Mabel was pulling out from the older man, significantly softer than she was before; the door cracked open. Bill turned his head sluggishly, narrowing his eye. Lana stood in the doorway, hand resting on the door handle and a look of shock on her face. Mabel eyed her lazily, rolling over on to her back beside Bill.

  
“How long have you been standing there?” Bill asked, tongue threatening to stick to the roof of his mouth. He was still so hot. Lana carefully entered the room and approached Bill, leaning down to press a hand to his forehead.

  
“Long enough to know that we need to get you two to your respective omegas.” She slipped a hand down his back, gently stroking it through his sweat-dampened shirt. Mabel snorted and rolled away from her. “Let's get you to the bath; I'll inform someone of Mabel's condition and have them move her to a spare room until Erin gets here.” She hauled Bill up, frowning as he winced.

  
Bill stood all the same, leaning heavily on the short woman. He was so thankful in times like these, that he'd found a nu to have as a friend. Having no interest in pheromones or sex, she was perfect for incidents like this.

  
“We shouldn't tell Dipper about this. Or Erin for that matter.” Bill muttered, stumbling in his walk and having to be steadied by Lana. “They'll have a fit.”

  
“Why, do you think that either will think less of you for bottoming?” Lana teased; Bill snorted, shaking his head. “Dipper isn't going to accuse you of cheating when you're in a rut.”

  
“Regardless, I'd rather not have either of them know. It's embarrassing. Two alphas easily fucking each other like that? We aren't betas, Lana. I can't believe that I gave in so easily to her.”

  
“Female alphas are scary. They have a sway over omegas and alphas alike, and that's nothing to be ashamed of.” She pet his chest. “I'll confirm with the Erin and Dipper that the two of you are in heat, and they'll be here in a couple hours. Think you can recoup enough in that time to prove it? I bet Dipper is thinking about how bad he wants to be underneath you right now.” Bill let out a soft snarl at her, nosing her hair playfully.

  
“Don't talk about him like that.” he told her, the warning in his voice obvious, despite his playful tone. Lana laughed at him, shaking her head. “But I've no doubt that as soon as I smell him, I'll be pinning him to the floor with the intent to fuck.”

  
“You better be. He's going to think you've got it pretty bad. Two heats and he hasn't realised yet, has he?” Lana told the alpha, cocking an eyebrow. Bill shrugged.

  
“I think he has, actually. He just hasn't brought it up; Dipper is probably trying to get it figured out entirely before he confronts me about it.” Lana briefly left Bill's side and let him rest on a nearby wall as she opened the bathroom door. “He's good about that kind of stuff.”

 

**Author's Note:**

> Thank you for reading!
> 
> Want to stay updated? Click [here](http://everyday-im-preaching.tumblr.com/) to stay in the know!


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